This is technically 2 features in one:

a) re-export @tsconfig/bases so that a user's tsconfig can, for example, "extends": "ts-node/node14/tsconfig.json"
b) in the absence of a tsconfig, check node version and use a suitable default.

https://github.com/tsconfig/bases

This allows ts-node to handle bare scripts using modern language features. For example, bigint literals require a modern "target" option which tsc does not adopt by default. If someone tried to write a ts-node shebang script using bigint literals, it would fail to compile unless they accompanied it with a tsconfig.json.

Note: changelog below mentions CLI and programmatic flags to disable this automatic base config.
Decided that was not necessary but put an implementation in #1249

TODO

• add CLI flag --skip-default-project
  • UPDATE decided to omit this feature until it is requested, per discord discussion below.
    Users can always create a tsconfig.json to suppress default project, or specify --compiler-options to override options)
• update programmatic option to match? skipDefaultProject?
  • not implemented, see rationale above
• what to name the CLI flag
  • https://discord.com/channels/508357248330760243/508357707602853888/814950988069732352
  • --no-implicit-project
  • --no-implicit-compiler-options
• extract CLI flag to another PR; do not implement it in this first pass
• add tests
• newer @tsconfig/bases are incompatible with Typescript 2.7: how to handle this?
  • can check ts.ScriptTarget and ts.libs to ensure they have the necessary entries. If node14 config is incompatible, try node12, then node10
  • TS 3.4 added target ES2019 but does not have the necessary require('typescript').libs entries for the node12 tsconfig, so checking libs is necessary